A virtual machine, including one or more guest operating systems and application programs, can be represented by a virtual-machine image file. Accordingly, virtual machines can be cloned and transferred using conventional file operations (duplicate, move, copy-and-paste).
Each virtual machine is self-contained in a virtual-machine image file. This file resides on a host machine. The virtual-machine image file can be copied and transferred, e.g., over a network. If the machine has to be moved from one physical location to another, it only requires copying the virtual machine image file from the host machine at the first location to another host machine at the second location over a computer network. However, as the virtual machine image files are very large, copying a virtual machine image requires a high bandwidth connection and can take a substantially long time.
While each virtual machine image file can take gigabytes to store, a large amount of the content in these virtual machine files is the same in many of them. This is due to the fact that today's software and operating systems are a monoculture. There are only a few variations of operating systems such as Windows XP™, Windows Vista™ and Redhat™ Linux. Additionally a handful of applications take up a large part of the application suite on each machine. Thus, it is observed that when a virtual machine image file is copied from one location to another, most of the information copied is already present in other virtual machine files at the destination.